Cancer arises in many instances in which a normal cell undergoes neoplastic transformation and becomes a malignant cell. Transformed (malignant) cells escape normal physiologic controls specifying cell phenotype and restraining cell proliferation. Transformed cells in an individual""s body thus proliferate, forming a tumor (also referred to as a neoplasm). When a tumor is found, the clinical objective is to destroy malignant cells selectively while mitigating any harm caused to normal cells in the individual undergoing treatment.
Currently, three major approaches are generally followed for the clinical management of cancer in humans and other animals. Surgical resection of solid tumors, malignant nodules and or entire organs may be appropriate for certain types of neoplasia. For other types, e.g., those manifested as soluble (ascites) tumors, hematopoeitic malignancies such as leukemia, or where metastasis of a primary tumor to another site in the body is suspected, radiation or chemotherapy may be appropriate. Either of these techniques may also be used as an adjunct to surgery.
Chemotherapy is often based on the use of drugs that are selectively toxic (cytotoxic) to cancer cells. Several general classes of chemotherapeutic drugs have been developed. A first class, antimetabolite drugs, includes drugs that interfere with nucleic acid synthesis, protein synthesis, and other vital metabolic processes. Another class, genotoxic drugs, inflicts damage on cellular nucleic acids, including DNA. Two widely used genotoxic anticancer drugs that have been shown to damage cellular DNA by producing crosslinks therein are cisplatin [cis-diamminedichloroplatinum(II)] and carboplatin [diammine(1,1-cyclobutanedicarboxylato)-platinum(II)]. Cisplatin and carboplatin currently are used in the treatment of selected, diverse neoplasms of epithelial and mesenchymal origin, including carcinomas and sarcomas of the respiratory, gastrointestinal and reproductive tracts, of the central nervous system, and of squamous origin in the head and neck. Cisplatin currently is preferred for the management of testicular carcinoma and in many instances produces a lasting remission. In cisplatin chemistry, one of the significant areas of research has involved the clinical difference, as exemplified in a variety of in vitro assays, indicating that trans-diamminedichloroplatinum(II) (trans-DDP) a regioisomer of cisplatin, is not an effective chemotherapeutic.
The repair of damage to cellular DNA is an important biological process carried out by a cell""s enzymatic DNA repair machinery. Unrepaired lesions in a cell""s genome may impede DNA replication, impair the replication fidelity of newly synthesized DNA or hinder the expression of genes needed for cell survival. Thus, genotoxic drugs generally are considered more toxic to actively dividing cells that engage in DNA synthesis than to quiescent, nondividing cells. Indeed, cells carrying a genetic defect in one or more elements of the enzymatic DNA repair machinery have been observed to be extremely sensitive to cisplatin. Normal cells of many body tissues, however, are quiescent and commit infrequently to reenter the cell cycle and divide. Greater time between rounds of cell division generally is afforded for the repair of DNA damage in normal cells inflected by chemotherapeutic genotoxins. As a result, some selectivity is achieved for the killing of cancer cells. Many treatment regimes reflect attempts to improve selectivity for cancer cells by co-administering chemotherapeutic drugs belonging to two or more of these general classes.
In some tissues, however, normal cells divide continuously. Thus, skin, hair follicles, buccal mucosa and other tissues of the gut lining, sperm and blood-forming tissues of the bone marrow remain vulnerable to the action of genotoxic drugs, including cisplatin. These and other classes of chemotherapeutic drugs can also cause severe adverse side effects in drug-sensitive organs, such as the liver and kidneys. These and other adverse side effects seriously constrain the dosage levels and lengths of treatment regimens that can be prescribed for individuals in need of cancer chemotherapy. Such constraints can prejudice the effectiveness of clinical treatment. For example, the drug or drug combination administered must contact and affect cancer cells at times appropriate to impair cell survival. Genotoxic drugs are most effective for killing cancer cells that are actively dividing when chemotherapeutic treatment is applied. Conversely, such drugs are relatively ineffective for the treatment of slow growing tumors. Carcinoma cells of the breast, lung and colorectal tissues, for example, typically double as slowly as once every 100 days. Such slowly growing tumors present difficult chemotherapeutic targets.
Moreover, cancer cells may acquire resistance to genotoxic drugs through diminished uptake or other changes in drug metabolism, such as those that occur upon drug-induced gene amplification or expression of a cellular gene for multiple drug resistance (MDR). Resistance to genotoxic drugs may also be acquired by activation or enhanced expression of enzymes in the cancer cell""s enzymatic DNA repair machinery. Therapies that employ combinations of drugs, or drugs and radiation, attempt to overcome these limitations. The pharmacokinetic profile of each chemotherapeutic drug in such a combinatorial regime, however, will in all likelihood differ. In particular, permeability of neoplastic tissue for each drug may be different. Thus, it may be difficult to achieve genotoxically effective concentrations of multiple chemotherapeutic drugs in target tissues.
In part, there remain a variety of needs to address many of the concerns discussed above. Some exemplary needs include: additional therapeutic agents with, for example, improved selectivity for destroying transformed cells in situ without significantly impairing viability of untransformed cells; enhancing effectiveness of therapeutic agents, such that satisfactory cell killing may be achieved with lower doses thereof; and therapeutic agents with improved selectivity for destroying transformed cells. The present invention provides therapeutic agents, and methods of making and using the same, that may address such concerns in certain embodiments. In certain embodiments of the subject invention, the therapeutic agents are coordination complexes that may be synthesized in a combinatorial fashion (in addition to other means). In addition to the foregoing embodiments, the coordination complexes of the present invention may be used for catalysis and other uses customary to coordination complexes.
In one aspect, the present invention provides methods for synthesizing a number of compounds of interest, such as transition metal-containing compounds and other coordination complexes. In certain embodiments, a library of coordination complexes may be prepared by combinatorial means that provides coordination complexes that exhibit diversity of structure and properties (e.g., chemical and biological). Utilizing combinatorial chemistry techniques, such as direct characterization, encoding, spatially addressing and deconvolution, the molecular identity of individual members of subject libraries may be ascertained in a screening format. In still other embodiments, the synthesis of compositions and libraries of them is partially or wholly automated.
In certain embodiments, the present invention provides methods for the production of coordination complexes and libraries of coordination complexes. In certain embodiments, the present invention provides synthetic strategies that allow production of large collections of coordination complexes. In still other embodiments, the coordination complexes of an inventive library are reminiscent of cisplatin in that they contain one or more atoms of platinum(II). In yet other embodiments, the subject coordination complexes may contain platinum(IV). The coordination complexes of such inventive libraries may possess the capability of acting as a therapeutic agent in a fashion similar to cisplatin.
In addition to providing coordination complexes, combinatorial libraries thereof, and methods of their production, the present invention also contemplates linkers and supports, which may be used in the preparation of support-bound coordination complexes and libraries.
In one subject method, coordination complexes of the present invention containing a metal may be prepared as follows using a method for identifying one or more coordination complexes comprising platinum in a library, comprising:
(a) chemically synthesizing a library, wherein a plurality of members of said library comprise coordination complexes comprising platinum;
(b) subjecting said members of said library to an assay; and
(c) comparing the response observed for any member of said library in said assay with the response of trans-DDP in said assay and the response of cisplatin in said assay.
Other exemplary embodiments of the subject invention are presented in the appended claims, which are incorporated by this reference in their entirety in this Summary of the Invention.
In another aspect, the present invention provides methods for identifying coordination complexes or other compositions that exhibit desirable properties. In certain embodiments of the present invention, a number of screening assays for the activity (e.g., biological, chemical, or catalytic) of subject coordination complexes may be determined and subsequently evaluated. Activities observed for subject coordination complexes may be compared to coordination complexes and other compositions having either desirable or undesirable properties in like assays.
For example, the present invention provides a method for determining one or more biological activities of a library member. In certain embodiments, the method for determining one or more biological activities of the inventive coordination complexes comprises contacting the inventive complexes with a biological target, such as a cell based assay, and determining a statistically significant change in a biochemical activity relative to the level of biochemical activity in the absence of the complex. One example of such a biochemical activity is the therapeutic index and other parameters relating to the efficacy and toxicity of any of the subject coordination complexes.
In one aspect, the present invention contemplates a variety of transcription-based assays to determine the biological activity of the subject compositions. In one embodiment, termed the CCF2/AM assay, the transcription of xcex2-lactamase is monitored by the use of the CCF2/AM dye and its fluorescence upon treatment with the agent of interest, usually a platinum-containing complex. Changes in fluorescence as compared to the background and control compounds indicate some form of biological activity on the part of the agent so as to disrupt transcription. In certain embodiments, the results of the assay for any subject coordination complex are compared to agents that are known chemotherapeutics, such as cisplatin, and those that are not, such as trans-DDP.
Another particular embodiment of the present inventive assays involves a method to assess whether a subject coordination complex, such as a platinum-containing coordination complex, forms lesions in DNA that are bound or otherwise recognized by a DNA structure specific recognition protein (xe2x80x9cSSRPxe2x80x9d). In certain embodiments, the present invention provides an in vitro assay for predicting whether a suspected genotoxic agent forms persistent genoric lesions in eukaryotic cellular DNA. In still other embodiments, the present invention provides a method of screening new coordination complexes for the ability to form DNA lesions that are bound by a SSRP. For example, the present invention provides a screening method for the rational design of new genotoxic agents that form persistent genomic lesions in eukaryotic cells. Methods such as these allow for high-throughput, in vitro assessment of drug candidate libraries produced by combinatorial chemistry.
Furthermore, the methods contemplated by the present invention may involve two or more assays, either the same assay or different assays, to identify coordination complexes that may produce xe2x80x9cfalse positivesxe2x80x9d in any single assay. In addition, the present inventive methods provide for positive and negative controls.
The present invention further provides a kit comprising a library of coordination complexes and reagents for determining one or more biological activities of a compound. To give but one example, the biological activity may be determined by providing a kit containing an appropriate assay and a library of coordination complexes. Kit components may be packaged for either manual or partially or wholly automated practice of the foregoing methods. In other embodiments involving kits, this invention contemplates a kit including compositions of the present invention, and optionally instructions for their use. Such kits may have a variety of uses, including, for example, imaging, diagnosis, therapy, vaccination and other applications.
In still another aspect, the present invention provides compositions including one or more of the coordination complexes identified by the subject method. The present invention additionally provides pharmaceutical compositions containing one or more library members. In certain embodiments, the pharmaceutical composition preferably comprises one or more of the inventive coordination complexes and a pharmaceutically acceptable carrier. In other embodiments, the present invention provides new therapeutic agents prepared by the inventive methods or identified by the inventive screening methods. In certain embodiments, those agents are coordination complexes. In still other embodiments, those agents contain the transition metal platinum.
In still another aspect, the compositions of the present invention, and methods of making and using the same, may be used in diagnostic applications, such as those embodiments in which the metal ion is suitable for imaging.
In another aspect, the compositions of the present invention may be used in the manufacture of a medicament for any number of uses, including for example treating any disease or other treatable condition of a patient. In still other aspects, the present invention is directed to a method for formulating coordination complexes of the present invention in a pharmaceutically acceptable carrier.
These embodiments of the present invention, other embodiments, and their features and characteristics, will be apparent from the description, drawings and claims that follow.